A rotatory device such as an electric motor or a generator may generate noise or electromagnetic interferences (EMI) during operation due to vibration of the rotatory device or due to commutation when brushes contact and traverse the gap(s) of the commutator. The vibrations or the engagement and disengagement between brushes and the commutator may cause unstable or less-than-desired electrical contact or variations in electrical conduction between the brushes and the commutator and thus cause noise or EMI.
A conventional rotatory device usually includes some decoupling capacitors disposed between the power source and ground to eliminate EMI or noise. Capacitors may nonetheless deviate from an ideal capacitor equation (e.g., a parallel-plate model for capacitors) in a variety of manners. For example, a capacitor may exhibit a non-linear or non-uniform behavior due to its dependence on temperatures such as operating or storage temperatures, aging effects, etc. Certain applications including the use of capacitors may also demand high temperature reliability or stability of these capacitors. Capacitors that exhibit stable or reliable capacitance at higher temperatures do exist. For example, mica or glass capacitors usually exhibit reliable and stable temperature performance. These capacitors that may tolerate higher temperatures are generally expensive for many applications. In addition or in the alternative, some applications may require components, including capacitors, to take less space or even as little space as practically possible or manageable to reduce the overall size of a package which may further lead to reduction in the production cost, while demanding the same performance characteristics.
Therefore, there exist a need for a rotatory device having one or more decoupling capacitors to effectively suppress noise or EMI, while exhibiting good stability or reliability during high temperatures without occupying valuable design space or increasing manufacturing costs.